Semiconductor devices are used in a variety of electronic applications, such as personal computers, cell phones, digital cameras, and other electronic equipment. Semiconductor devices are typically fabricated by sequentially depositing insulating or dielectric layers, conductive layers, and semiconductive layers of material over a semiconductor substrate, and patterning the various material layers using lithography to form circuit components and elements thereon.
Sulfuric acid (H2SO4) is utilized in large quantity in various kinds of industries with a grade (at a purity or a concentration) determined according to the purposes of the industries. In the case that such sulfuric acids are spent, various methods for recycling the sulfuric acids have been proposed.
Although existing recycling methods have been generally adequate for their intended purpose, they have not been entirely satisfactory in all aspects.